Sidenote: I have no idea what Pioneer drives are actually reporting, but it is definitely not PIsum8 nor PIF(sum1), and DVDInfoPro is somehow scaling the values to raise the impression that it could do something like PIsum8.

The bushound log made with a really crappy disc even contains values more than twice as high as the maximum value of 1664 for PIsum8, so it either is PIE over a range longer than 16 sectors, or it even is the number of bytes that were bad. In the latter case, it would be a shame for DVDInfoPro to claim that it could get PIsum8 from that information... but I can't be sure about that. I am only sure that it definitely is not PIsum8

DVD-Speed *seemed* to report the values reported by the drive without modification